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Schiavon D.,OSRAM | Schiavon D.,University of Ulm | Binder M.,OSRAM | Binder M.,Fraunhofer Institute For Angewandte Festkorperphysik | And 2 more authors.
Applied Physics Letters | Year: 2013

We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/GaN light-emitting diode (LED) is converted into green light by an optically pumped GaInN/GaN multiple quantum well structure. This solution reached an efficacy of 127 lm/W, i.e., higher than that of state-of-the-art 1 mm2 GaInN/GaN LEDs emitting directly at the target wavelength, at 350 mA current and 535 nm peak wavelength. Optically pumped converters overcome the design limitations of typical multiple quantum well LEDs, where carrier transport issues limit the maximum number of functioning wells and might help to solve the problem of the green gap. © 2013 American Institute of Physics.

Binder M.,OSRAM | Nirschl A.,OSRAM | Nirschl A.,University of Regensburg | Zeisel R.,OSRAM | And 6 more authors.
Applied Physics Letters | Year: 2013

We report the direct observation of hot carriers generated by Auger recombination via photoluminescence spectroscopy on tailored (AlGaIn)N multiple quantum well (QW) structures containing alternating green and ultra-violet (UV) emitting (GaIn)N QWs. Optically pumping solely the green QWs using a blue emitting high power laser diode, carrier densities similar to electrical light-emitting diode (LED) operation were achieved, circumventing possible leakage and injection effects. This way, luminescence from the UV QWs could be observed for excitation where the emission from the green QWs showed significant droop, giving direct evidence for Auger generated hot electrons and holes being injected into the UV QWs. An examination of the quantitative relation between the intensity of the UV luminescence and the amount of charge carriers lost due to drooping of the QWs supports the conclusion that Auger processes contribute significantly to the droop phenomenon in (AlGaIn)N based light-emitting diodes. © 2013 AIP Publishing LLC.

Minkevicius L.,Lithuanian Academy of Sciences | Tamosiunas V.,Lithuanian Academy of Sciences | Kasalynas I.,Lithuanian Academy of Sciences | Seliuta D.,Lithuanian Academy of Sciences | And 5 more authors.
Applied Physics Letters | Year: 2011

Room-temperature detection and imaging in transmission and reflection geometries at 0.591 THz with planar asymmetrically shaped InGaAs diodes (also called bow-tie diodes) are demonstrated in direct and heterodyne mode. The sensitivity of the diodes is found to be 6 V/W in direct mode, and the noise-equivalent power (NEP) in direct and heterodyne mode is estimated to be about 4 nW/√Hz and 230 fW/Hz for a local-oscillator power of 11 μW, respectively. The improvement of the dynamic range by heterodyning over direct power detection amounts to about 20 dB using pixel read-out times relevant to real-time imaging conditions. © 2011 American Institute of Physics.

Zybell S.,Helmholtz Center Dresden | Schneider H.,Helmholtz Center Dresden | Winnerl S.,Helmholtz Center Dresden | Wagner M.,Helmholtz Center Dresden | And 2 more authors.
Applied Physics Letters | Year: 2011

We investigate the time-resolved photoluminescence (PL) dynamics of an undoped GaAs/AlGaAs multiple quantum well under mid-infrared (MIR) irradiation. A time-delayed MIR laser pulse from a free-electron laser, tuned to the intersubband transition energy of the quantum well, induces temporal quenching of the PL intensity with subsequent recovery. The experimental data can be accurately described by a simple rate-equation model, which accounts for the cooling of the non-radiative states to radiative states. By performing polarization sensitive measurements, we are able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is about 50 times more efficient. © 2011 American Institute of Physics.

Worl A.,Fraunhofer Institute For Angewandte Festkorperphysik | Rehm R.,Fraunhofer Institute For Angewandte Festkorperphysik | Walther M.,Fraunhofer Institute For Angewandte Festkorperphysik
Infrared Physics and Technology | Year: 2013

We characterize the low-frequency white noise behavior of a large set of InAs/GaSb superlattice infrared pin-photodiodes for the mid-wavelength infrared regime at 3-5 μm. For diodes with an increased dark current in comparison to the dark current of generation-recombination limited bulk material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre's noise model for avalanche multiplication processes is compliant with our data. We suggest that within high electric field domains localized around macroscopic defects, avalanche multiplication processes leading to increased dark current and excess noise. © 2013 Elsevier B.V. All rights reserved.

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